Novel styrene polymers functionalized with phosphorus–nitrogen containing molecules: Synthesis and properties

A phosphorus and nitrogen-containing compound with high phosphorus content, AC₂NP₂, was firstly synthesized by the Kabachnik–Fields reaction and followed by esterification with acryloyl chloride. The synthesized comonomer was then incorporated into different amounts of polystyrene via radical solution polymerization. The copolymers were well characterized using Fourier transform infrared (FTIR), UV/vis spectrophotometer, nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), microscale combustion calorimeter (MCC) and LOI. The results showed that the AC₂NP₂ was easily incorporated into the backbone of polystyrene, and the copolymers prepared have high transparency. The glass transition temperature (T_g) of the copolymers was decreased with increasing the AC₂NP₂ content, due to the introduction of much more flexible molecular chain. The TGA results revealed that the introduction of AC₂NP₂ units slightly decreased the initial decomposition temperatures, but significantly improved the thermal stability of copolymers at high temperature regions under both nitrogen and air atmosphere. Furthermore, all the copolymers exhibited much lower flammability as compared with virgin polystyrene.     

Evaluation of crack nucleation site and mechanical properties for friction stir welded butt joint in 2024-T3 aluminum alloy

In this paper, metallographic observations, hardness measurement, and static and fatigue tests were conducted to investigate the discontinuity states which become crack nucleation sites in friction stir welded butt joints in 2-mm-thick 2024-T3 aluminum alloy and static and fatigue properties of the joint. Because different types of surface finish can be used depending on the application of the joint, several types of surface conditions were tested to evaluate their effect on crack nucleation sites and static and fatigue life. Indentation hardness tests revealed that typical hardness reduction is not necessarily observed on the section of the welding line. Based on fatigue test results, it was confirmed that there are several types of crack nucleation sites for friction stir welding (FSW) joints depending on the surface finish, and the features of the fracture surface also differ depending on the site. Furthermore, the type of discontinuity state affects the fatigue life of the FSW joint.     

Fast Calculation of Field Currents and Reactances for Doubly Fed Generators With Rotor Duct Pieces

Doubly fed generators have been used as adjustable-speed pumped-storage generator motors and wind turbine generators. Accurate determination of field currents and reactances is important for the design of these machines. We propose a calculation method to obtain the field currents and reactances of machines with rotor duct pieces under any steady-state balanced load condition. The method links two-dimensional static finite-element analysis (FEA) with an approximate calculation to consider three-dimensional (3-D) skin effect in the duct pieces. Its advantage is that the computational time is much smaller than 3-D transient FEA when the slip frequency is not zero. The method will contribute to improvement of the design of doubly fed generators with rotor duct pieces. It was applied to a 395 MVA machine, and the calculated field currents agreed well with the measurements. Variation in the reactances due to saturation is also discussed     

Energy transport simulation for graded HBT's: Importance of settingadequate values for transport parameters

An energy transport simulation method for graded AlGaAs/GaAs heterojunction bipolar transistors (HBTs) is presented in which Al composition-, doping density-, and energy-dependences of transport parameters are considered. For several representative Al composition and doping densities, parameters such as electron mobility, energy relaxation time, and upper-valley fraction are evaluated as a function of electron energy by a Monte Carlo method. For the other Al composition, these are determined by a linear interpolation method. Calculated cutoff frequency characteristics and electron velocity profiles are compared with those obtained by using more simplified approaches, demonstrating the importance of giving adequate transport parameters, particularly in analyzing graded band-gap base HBTs     

Widely tunable Ce- and Er-codoped fluorozirconate fiber laser with 975-nm laser diode pumping

A spectrally narrowed widely tunable Ce/sup 3+/: Er/sup 3+/-codoped fluorozirconate (ZBLAN) fiber laser with a continuous-wave laser diode pumping at 975-nm pumping is demonstrated. Wide tunable range over 120 nm (1490-1610 nm) is attained by using a diffraction grating combined with a tuning mirror in the Ce/sup 3+/: Er/sup 3+/-ZBLAN fiber laser cavity. Rate-equation model analysis shows that the tunable range can expand further by using a wavelength-dependent reflectivity cavity mirror.     

2.44-GFLOPS 300-MHz floating-point vector-processing unit forhigh-performance 3D graphics computing

A vector unit for high-performance three-dimensional graphics computing has been developed. We implement four floating-point multiply-accumulate units, which execute multiply-add operations with one throughput; one floating-point divide/square root unit, which executes division and square-root operations with six cycles at 300 MHz; and one vector general-purpose register file, which has 128 bits×32 words. The parallel execution of all units delivers a peak performance of 2.44 GFLOPS at 300 MHz     

The effect of the molecular structure of a cationic azo dye on the photoinduced intercalation of phenol in a montmorillonite

The effect of the molecular structure of a cationic azo dye on the photoinduced intercalation of phenol into the azo dye-montmorillonites was reported. Two types of cationic azo dyes were used; one has (2-hydroxyethyl)dimethylammonium group (AZ(OH)⁺), and the other has trimethylammonium group (AZ(CH₃)⁺). Phenol was intercalated into both cation exchanged azo dye-montmorillonites (Kunipia F) by mechanical mixing without solvent. By the UV irradiation, the basal spacings increased further, and subsequent visible light irradiation led to decrease the basal spacings, indicating the intercalation and the deintercalation of phenol by the UV and visible light, respectively. The amounts of the phenol intercalated both chemically and photochemically varied depending on the azobenzene cations, showing the interactions between the cationic head group and phenol.     

Ice storage system with water–oil mixture: formation of suspension with high IPF

A new method of forming ice, which is one of the dynamic types of ice storage system, is studied. In the method a water-oil emulsion is cooled with stirring in a vessel and changed into an ice-oil and water suspension. A mixture of 10 vol% silicone-oil and 90 vol% water is emulsified with a small amount of an additive. Silane-couplers are tested as the additive and effects of the additive on ice formation process are investigated. Cooling rate is changed and vessels made of various materials are tested. It is proved that the present method has the following characteristics. Ice–oil and water suspension (slush ice) which has a good fluidity is able to be formed without adhering to the cooling surface. Ice in the suspension is granular and dispersed state and the suspension with more than 70% of ice packing factor (IPF) is also able to be formed. The suspension with the high IPF can be preserved for a long time in the granular state.     

Inductance-controlled electroabsorption Modulator modules using the flip-chip bonding technique

The wire-bonding technique is widely used for the connections between the electroabsorption (EA) modulator chips and the electrical signal transmission lines. However, the parasitic inductance of the bonding wire degrades the electrical characteristics of the EA modulator modules in a high-frequency region. In this paper, we theoretically analyze the influence of parasitic inductance on the base-band digital transmission and obtain the relationship between the EA modulator capacitance and the optimum lead inductance. For precise inductance control, we introduced the flip-chip bonding (FCB) technique and fabricated 40-Gb/s EA modulator modules.